This is a proposal to study the effects of a patient-centered, computer- based support system on the health care costs and quality of care of HIV- infected men and women, including IVDU's. The system, called CHESS (Comprehensive Health Enhancement Support System) is a computer-based system which provides information, referrals, skills training, decision support, and social support on a wide range of HIV-related topics. A previous study of CHESS with HIV-positive patients has shown it to be accepted and heavily used, with significant effects on quality of life. Preliminary evidence was also obtained that the system may also reduce some types of health care costs. The proposed research provides CHESS to subjects for a longer period of time and will integrate more detailed and precise interview data with medical and pharmacy records to get an expanded picture of CHESS impact on health care costs, quality, and compliance. It is hypothesized that through its education, analysis and social support services, CHESS will reduce health care costs and increase quality of care through: I) increased prophylaxis for preventable infections; 2) early detection and intervention in infections and side effects of treatment; 3) reduced unnecessary phone calls and visits; and, 4) increased compliance with prescribed treatments. A total of 300 subjects including 60 IV Drug Users, with advanced HIV infection (a CD4 count of < 200) will be recruited from the two largest providers of health care to HIV-infected patients in Wisconsin. IV Drug Users will be recruited by the organization in Wisconsin providing support to IV Drug Users. Subjects will be randomly assigned to experimental (in- home use of CHESS for 1 year) or control (no intervention) groups. Through interviews with subjects and detailed extraction of data from medical and billing records, the impact of CHESS on the following areas will be analyzed: I) costs of treated specific AIDS-related infections and side effects of treatment; 2) severity of infections and side-effects; 3) quality of life; 4) unscheduled visits and phone calls; and, 5) treatment compliance. Additional analyses will examine the differential impact of CHESS on IvDU vs. non-IVDU patients. Preliminary studies of CHESS involving HIV-infected women have suggested that CHESS may have an even greater impact on women than on men. Thus, this study will also compare the effects of CHESS on women versus men on the above criteria.